Meta: update upload-artifact action prior to deprecation (#3506)

See https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

.github/workflows/preview-build.yml

@@ -19,7 +19,7 @@ jobs:
       - run: npm run build-only
       - run: node scripts/insert_snapshot_warning
       - run: echo ${{ github.event.number }} > out/pr.txt
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: out
           path: out/